To date, serial-communication-method communication apparatus utilizing an SPI has been widely utilized, and various kinds of methods therefor have been proposed. For example, in Patent Document 1, there is proposed a communication circuit including a reception unit that serially receives, as a set of input data pieces, a command and a synchronization identification code that is different from the command and a determination unit that receives the synchronization identification code from the reception unit and gives an instruction of starting implementation of response processing based on the command when the synchronization identification code coincides with a predetermined value; the configuration of this communication circuit makes it possible to apply this communication circuit to a 3-line SPI having three serial-communication terminals or a 4-line SPI having four serial-communication terminals; thus, it is allegedly claimed that a high-reliability serial communication circuit and the like can be realized.